How Does Tig Welding Work?
Tig welding is a form of welding that uses a tungsten electrode as the filler wire. It is often used for high-quality welds that require tight tolerances and cast iron and nickel alloys. The technique requires shielding gas to protect the molten pool from the air, which can cause porosity in the finished weld. Also, it is not recommended to mix tungsten electrodes of different diameters, resulting in inconsistent weld quality.
The Tig Welding Process – How It Works?
1. Preparing The Electrode
The welding procedure requires the welder to preheat the tungsten electrode with shielding gas. This shielding gas is composed of Nitrogen in the form of Argon at a pressure of 1.5-2.0 atmospheres and a temperature of 1,350 to 1,450 degrees Fahrenheit (765 to 810 degrees Celsius). These parameters create an inert atmosphere that is needed to protect the molten pool from oxygen. Also, when shielding gas is sprayed on the tungsten electrode, it fills in the air bubbles that exist within the molten pool.
The tip of the electrode should be cleaned with a Borazon cloth before starting. This helps to remove any oxide build-up that is present on the tip of the electrode. It also helps to ensure that the molten pool is clean and will not contain any impurities.
2. Making The Arc
After the shielding gas is sprayed on the tungsten electrode, it is introduced into the molten pool with a solid tungsten wire. The arc is ignited by inserting the exposed tungsten electrode into the molten pool. Then, the shielding gas is turned up to about 50% power. This removes most of the oxygen from within the molten pool and helps form a stable arc.
3. Extending The Arc
The welder makes a “W” motion to extend the arc. This forms a cone-shaped puddle in the molten pool, wherein more material is added until it reaches the end of the joint that is being welded. The extension of the arc gradually increases its heat and power, thereby increasing its penetration rate into the weld pool. This helps produce a more consistent weld bead with a smooth surface finish and a complete fusion between base and filler metal.
4. Cooling The Arc
After the arc is extended, it must be cooled to prevent burning through any part of the weld pool. This is done by twisting the electrode slightly and increasing its distance from the weld pool. This will reduce the current flowing through the arc, thereby preventing its premature termination.
5. Repairing Damaged Weld Metal
Damaged spots can be quickly repaired by striking the electrode into the molten pool with a “V” motion. This helps in keeping the weld pool clean and free from damage.
6. Maintaining A Clean Surface Finish
The surface finish of a weld is important as it determines its strength, appearance, and longevity. However, it is quite difficult to maintain a smooth surface finish when welding with tungsten electrodes. This is because these electrodes tend to leave an orange rust trail when they are retracted from the weld pool. However, this can be remedied by using a stainless steel electrode.
Benefits of Tig Welding
1. Cost
The cost of tig welding is lower than that of other welding processes mainly because it uses smaller electrodes. This means that filler metal is low in quantity and does not require much power to weld.
2. Thinner Wall Weld
Tig welding is generally used for welding thinner metals than other welding techniques. The ability to weld thinner metals makes it a faster and cheaper way to produce parts.
3. Mass Production
Tig welding is suitable for mass production because of its ability to weld thick and thin walls. It can also be coupled with other processes such as CO2-tig welding, puddle-tig or gas metal arc welding (GMAW) to increase production rates without compromising quality.
Drawbacks of Tig Welding
1. Slow Production Rates
Because of the low power requirements and limited filler metal use, tig welding is not suitable for quickly welding large parts compared to GMAW or SAW (submerged arc welding).
2. High Cost Of Equipment
Tig equipment is considerably more expensive than other welding processes. This is because tig equipment requires a high initial investment but less operating costs.
3. Slower Welding Speeds
One of the major drawbacks of tig welding is that it cannot weld thin metals quickly due to its slow welding speeds. However, this is compensated by its ability to use smaller electrodes and therefore produce smoother welds with a thinner welding bead.
Tips to Manage a Proper Tig Welding Process
1. Practice your technique and weld on scrap metal first before welding on workpieces.
2. Remember to use the right diameter of filler metal based on the thickness of your workpiece.
3. Always use a clean and sharp tungsten electrode free from any scratches or oil buildup. A sharp tip will help reduce heat input and avoid incomplete filler wire penetration in the weld joint.
4. Keep the arc sharp and clean by adjusting the angle of engagement with the workpiece.
5. Use overlapping welding motions and travel continuously over the weld joint to achieve a good penetration rate.
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Conclusion
Tig welding is an excellent welding technique that produces high-quality welds that are smooth and beautiful. It is one of the most efficient methods used in manufacturing due to its low cost and greater production rates. However, it is not suitable for all metals and welding conditions.
